Image-displaying device and method for controlling image-displaying device

ABSTRACT

An image capturing device includes an image capturing unit capturing an image at a timing based on a first frame rate and outputs data corresponding to the image after a first period, an image data generation unit generating image data based on the output data and outputting the image data after a second period, a display unit displaying a display image based on the image data after the second period and at a timing based on a second frame rate, and a mode selecting unit selecting a first or second mode. The first mode prioritizes reduction in a display delay time. The second mode prioritizes image quality of the display image over reduction in the display delay time. A total period of the first and second periods is less than or equal to a first vertical synchronization period based on the first frame rate when the first mode is selected.

CROSS-REFERENCE TO RELATED APPLICAT1ONS

This is a continuation application of U.S. patent application Ser. No.14/1966,729 filed on Dec. 11, 2015, which is a continuation applicationof U.S. patent application Ser. No. 14/511,335 filed on Oct. 10, 2014,now U.S. Pat. No. 9,241,108, which is a continuation application of U.S.patent application Ser. No. 13/683,628 filed on Nov. 21, 2012, now U.S.Pat. No. 8,860,864. This application claims priority to Japanese PatentApplication No. 2012-244183 filed on Nov. 6, 2012. The entire disclosureof Japanese Patent Application No. 2012-244183 is hereby incorporatedherein by reference.

BACKGROUND

Technical Field

The present invention relates to an image capturing device and a methodfor controlling an image capturing device, and particularly relates to atechnique for reducing display delay time in a live view.

Related Art

Conventionally, as disclosed in Japanese Laid-open Patent PublicationNo. 2007-295401 or Japanese Laid-open Patent Publication No. 2000-92380,an image capturing device has been known in which an image captured byan image capturing sensor is displayed as a live view on a displaysection such as a liquid crystal display.

SUMMARY

In an image capturing device in which a live view is displayed, it isknown that there is a delay in displaying an image of an object withrespect to the object. The display delay time can be defined as timerequired for displaying image data that shows an image of the object ona display section after an image capturing sensor receives light thatshows the image of the object and stores it as a charge. In thisdefinition, the display delay time includes charge storing time andprocessing time required for generating image data for a display anddisplaying it based on an output of the image capturing sensor. Sincethe charge storing time is generally determined by AE processingcorresponding to the image capturing environment, it has been consideredthat the display delay time can be reduced by reducing the processingtime. Also, in order to further reduce the display delay time, it isconsidered that the charge storing time should be reduced.

Japanese Laid-open Patent Publication No. 2007-295401 disclosed inparagraphs 0094-0097 that the frame rate is determined corresponding tothe image capturing environment after the gain of the sensor and thediaphragm are set, and the charge storing time may be set optionally aslong as it is shorter than time corresponding to the frame rate (avertical synchronization period). Also, Japanese Laid-open PatentPublication No. 2000-92380 (FIG. 2) disclosed that the charge storingtime is made as long as possible (a maximum amount of time to such anextent not to cause dropped frames, paragraph 0003) in a live viewdisplay, and the gain of the sensor is increased if it is still dark.This document also disclosed that, in capturing an image for the record,the charge storing time in which the gain is restored is determined in acase where the gain has been increased (the charge storing time in whichthe gain is restored is longer than that of the case where the gain isincreased), and image capturing is conducted with the charge storingtime in which the gain is restored. Accordingly, it has beenconventionally known that the charge storing time may eventually becomeshorter than the vertical synchronization period in a live view display.However, it is not that the charge storing time is determined so as tointentionally reduce the display delay time. Therefore, when the chargestoring time that achieves an appropriate exposure by AE processing hasthe same length as the vertical synchronization period, for example, thecharge storing time is not shorter than the vertical synchronizationperiod plus the processing time.

The present invention has been made to address the above-describedcircumstances, and an object of the present invention is to reduce thedisplay delay time in a live view display.

An image capturing device according to one aspect includes an imagecapturing unit, an image data generation unit, a display unit, and amode selecting unit. The image capturing unit captures an image at atiming based on a first frame rate of the image capturing unit andoutputs output data corresponding to the image after a first period. Theimage data generation unit generates image data based on the output dataand outputs the image data after a second period after the first period.The display unit displays a display image based on the image data afterthe second period and at a timing based on a second frame rate of thedisplay unit. The mode selecting unit selects a first mode or a secondmode. The first mode prioritizes reduction in a display delay time ofthe display image. The second mode prioritizes image quality of thedisplay image over the reduction in the display delay time. A totalperiod of the first period and the second period is less than or equalto a first vertical synchronization period based on the first frame ratewhen the first mode is selected.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a block diagram showing a configuration of an image capturingdevice.

FIG. 2 is a flow chart showing image capturing processing.

FIG. 3A is a diagram showing a display screen, and FIG. 3B is a timingchart for explaining a charge storing timing and a display timing.

FIG. 4 is a program diagram according to a first embodiment.

FIG. 5 is a timing chart showing image capturing and a display for alive view.

FIG. 6A and FIG. 6B are program diagrams according to anotherembodiment.

FIG. 7 is a program diagram according to another embodiment.

FIG. 8A and FIG. 8B are timing charts according to another embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the attached drawings. The corresponding components in therespective drawings are given the same reference numerals and theoverlapping explanations are omitted.

1. First Embodiment 1-1. Configuration of Image Capturing Device

FIG. 1 is a block diagram showing a configuration of an image capturingdevice 1 according to an embodiment of the present invention. The imagecapturing device 1 is a mirror-less digital camera provided with an EVF(Electronic View Finder). The image capturing device 1 according to thepresent embodiment has a lens unit 10, a shutter 13, a shutter controlsection 50, an image capturing sensor 14, a buffer 15, an imageprocessing section 80, a timing control section 60, a display section20, a recording section 30, an operating section 40, a CPU 70, a RAM 71,a ROM 72, and the like. The CPU 70 executes a program recorded in theROM 72 by using the RAM 71 as appropriate. Through the function of theprogram, the CPU 70 generates image data that shows an object capturedby the image capturing sensor 14 in response to an operation to theoperating section 40, and implements the function to display on thedisplay section 20 or record on a removable memory. A plurality of kindsof program diagrams for live view image capturing or actual imagecapturing are recorded in the ROM. The operating section 40 has ashutter button, a dial switch for changing charge storing time (shutterspeed) or an aperture of a diaphragm 12, a switch for changing ISOsensitivity, and a switch for operating various kinds of setting menus.

The lens unit 10 has a lens 11, the diaphragm 12, a lens driving section1 la, a diaphragm driving section 12 a, and the like. The lens unit 10is attached to a case of the image capturing device 1 in a replaceablemanner. The case is not shown in the drawing. The lens 11 is illustratedas a single lens in FIG. 1 for simplicity. However, the lens 11 includesa plurality of lenses arranged in an optical axis direction, and eachlens is supported by an outer edge portion thereof. The lens drivingsection 11 a adjusts a focus or a zoom magnification by moving at leastone lens in the optical axis direction in response to a control signaloutput from the CPU 70. The diaphragm 12 is composed of a plurality oflight shielding plates that can change the aperture. The diaphragmdriving section 12 a changes the aperture of the diaphragm 12 by drivingthe diaphragm 12 in response to a control signal output from the CPU 70.

The shutter 13 is a mechanical focal-plane type shutter, and is providedwith a plurality of openable (folding) light shielding curtains as alight shielding section having a plane plate shape in parallel with animage capturing sensor plane of the image capturing sensor 14. The lightshielding curtains are configured to move in a direction perpendicularto the optical axis in response to a control signal from the shuttercontrol section 50. Normally, the light shielding curtains are retainedwithout interrupting a light path in a direction in parallel with theoptical axis. When a predetermined trigger is given in a state where thelight shielding curtains are retained without interrupting a light path,the state where the light shielding curtains are retained withoutinterrupting a light path is released, and the light shielding curtainsare driven in the direction perpendicular to the optical axis so as toplace a plurality of vanes thereof in a state of interrupting the lightpath. In FIG. 1, the moving direction of the light shielding curtains isshown by a dashed arrow Am.

The image capturing sensor 14 is a CMOS (Complementary Metal OxideSemiconductor) image sensor provided with a color filter of a Bayerarray and a plurality of photoelectric conversion elements (photodiodes) which store a charge corresponding to the amount of light ineach pixel by photoelectric conversion. The image capturing sensor maybe another sensor such as a CCD (Charge Coupled Device) image sensor.The positions of the pixels of the image capturing sensor 14 are definedin coordinates of a Cartesian coordinate system. A line is formed with aplurality of pixels arranged in a direction parallel to one axis ofcoordinate, and a plurality of lines are arranged in a directionparallel to the other axis of coordinate. In the present specification,the direction parallel to the line is referred to as a horizontaldirection, and the direction perpendicular to the line is referred to asa perpendicular direction. The image capturing sensor 14 is disposedsuch that the perpendicular direction is in parallel with the movingdirection (Am) of the shutter 13.

In the image capturing sensor 14 of the present embodiment, it ispossible to reset (discharge) charges stored in the photoelectricconversion elements per line. Specifically, charges are reset at thesame time with respect to each other in the plurality of photoelectricconversion elements that belong to the same line, and charge storing isstarted at the same time with respect to each other immediately afterthe reset is released. The image capturing sensor 14 reads out thecharges stored in the photoelectric conversion elements per line. Theimage capturing sensor 14 can conduct partial readout by reading out “M”lines per “N” lines (“N” and “M” are natural numbers that satisfy N>M)corresponding to a required image quality or speed instead of readingout all the lines. In the photoelectric conversion elements, charges arein a state of being reset even when the charges are read out.

In the image capturing sensor 14, the gain (corresponding to ISOsensitivity) with respect to a value of reading out the charge storingamount of a pixel can be adjusted in response to a control signal fromthe CPU 70. Specifically, it is possible to gradually change the degreeof amplification of a signal that shows charges stored in thephotoelectric conversion elements. The image capturing sensor 14conducts A/D conversion to a tone value of an exposure amountcorresponding to the charge that has been read out by an A/D convertorand the like, and generates 14-bit (at least 10-bit) output data that isassociated with each pixel. The output data that has been read out fromthe image capturing sensor 14 is stored in the buffer 15, and variouskinds of image processing is conducted to the output data by the imageprocessing section 80 as described below.

The timing control section 60 has a sensor control section 61 and adisplay control section 62. The sensor control section 61 generates asignal for controlling various kinds of operation timings of each of thephotoelectric conversion elements, and outputs it to the image capturingsensor 14. More specifically, the sensor control section 61 outputs avertical synchronization signal (SVsync) that defines a period (verticalsynchronization period) to read out detection results of thephotoelectric conversion elements in one frame, a horizontalsynchronization signal (SHsync) that defines a period (horizontalsynchronization period) to read out detection results of thephotoelectric conversion elements in one line, a data clock signal(SDotclock) that defines a timing and the like to read out image data ofeach pixel, and a reset signal (SHreset) that defines a timing todiscard charges of the photoelectric conversion elements in acorresponding line, for example. The image capturing sensor 14 startsoutputting output data of one frame in response to the verticalsynchronization signal SVsync, and sequentially reads out output data(SD) that shows detection results of the photoelectric conversionelement corresponding to the pixel of the image capturing sensor 14 at atiming in response to the data clock signal SDotclock within a perioddefined by the horizontal synchronization signal SHsync. The imagecapturing sensor 14 discards charges of the photoelectric conversionelements in a designated line at a timing in response to the resetsignal SHreset. The CPU 70 and the sensor control section 61 correspondto the “control unit”.

The display control section 62 generates a signal for controllingdisplay timings of various kinds of display pixels of the displaysection 20, and outputs it to the display section 20. The displaysection 20 is an EVF, which displays image data generated based on theoutput data of the image capturing sensor 14 as a live view (movingimage), and displays a still image of an object that has been actuallycaptured. The display section 20 has an interface circuit, a liquidcrystal panel driver, a liquid crystal panel, an eye lens, and the like,which are not shown in the drawing. The liquid crystal panel driveroutputs a signal for driving liquid crystal by applying a voltage toeach sub-pixel to the liquid crystal panel. The liquid crystal paneldriver is configured to output various kinds of signals for a display onthe liquid crystal panel such as a vertical synchronization signal(DVsync) that defines a period to display one frame, a horizontalsynchronization signal (DHsync) that defines a period to display oneline, a data active signal (DDactive) that defines a period to take inimage data in each line, a dot clock signal (DDotclock) that defines atiming and the like to take in image data of each pixel, and image data(DD) of each pixel. The vertical synchronization signal DVsync, thehorizontal synchronization signal DHsync, the data active signalDDactive, and the data clock signal (DDotclock) are generated by thedisplay control section 62, and output to the display section 20.

In the present embodiment, the output timing of the horizontalsynchronization signal DHsync is variable. As described below, after thedisplay control section 62 acquires progress information showing that anext display target line is ready to be displayed from an image datageneration section 81, the display control section 62 outputs thehorizontal synchronization signal DHsync, and the display of the nextdisplay target line is started. It is sufficient for the progressinformation to be information that allows the display control section 62to determine that image data of an N^(th) line (“N” is a natural number)is ready to be displayed when the next display target line is the N^(th)line, and various embodiments are possible. For example, the progressinformation may be a pulse signal that is output from the image datageneration section 81 to the display control section 62 at a timing whenprocessing of a resizing processing section of the image data generationsection 81 is finished and image data of the N^(th) line is generated.Alternatively, for example, the progress information may be a pulsesignal that is output at a timing when generation of image data of theN^(th) line is finished and writing of the image data of the N^(th) linein the buffer 15 is finished. Alternatively, for example, the progressinformation may be a pulse signal that is output at a timing whengeneration of image data from the N^(th) line to the (N+i)^(th) line(“i” is a natural number), not only image data of the N^(th) line, isfinished and writing of the image data from the N^(th) line to the(N+i)^(th) line in the buffer 15 is finished. Alternatively, forexample, the progress information does not need to be output as a pulsesignal at the above-described timings, and may be information of anotherembodiment showing that image data has been forwarded to a predeterminedbuffer (for example, a value of a counter for counting the number oflines that have already been forwarded and the like). Alternatively, forexample, a combination of a counter value and a pulse signal that isdescribed next may be treated as the progress information. In such acase, the counter is, for example, a counter that shows the value of “N”by counting up at a timing when processing of the resizing processingsection of the image data generation section 81 is finished and imagedata of the N^(th) line is generated. Also, in such a case, the pulsesignal is, for example, a pulse signal that is output to the displaycontrol section 62 to show that the counter value has been changed whenthe counter counts up at the above-described timing. The timing in thedisplay control section 62 may be generated when the display controlsection 62 acquires a counter value showing a line in which generationof image data has been finished (showing to which line generation hasbeen finished) and a pulse signal showing the timing when the counterhas been renewed.

The present embodiment treats the pulse signal that is output at atiming when generation of image data of the N^(th) line is finished andwriting of the image data of the N^(th) line in the buffer 15 isfinished as the progress information.

The image processing section 80 is provided with the image datageneration section 81. The image data generation section 81 conductsvarious kinds of image processing through pipeline processing withrespect to the output data SD output from the image capturing sensor 14by using a line buffer or a frame buffer that has been obtained in thebuffer 15 beforehand. The image processing section 80 is an SOC that isconstructed by an ASIC or a DSP, for example. The image data generationsection 81 has a pixel interpolation section, a color reproductionprocessing section, a filter processing section, a gamma correctionsection, the resizing processing section, and an image data outputsection. The image data generation section 81 can generate the imagedata DD per line based on the output data SD of the image capturingsensor 14.

More specifically, the image data generation section 81 acquires theoutput data SD output by the image capturing sensor 14 from the linebuffer of the buffer 15. The pixel interpolation section calculates atone value of two channels of color different from the color of thecolor filter provided in the photoelectric conversion elementcorresponding to each pixel by conducting interpolation processing to atarget pixel using a tone value of a peripheral pixel of the targetpixel. As a result, data in which three channels of tone values areassociated with each pixel is generated. The color reproductionprocessing section conducts color conversion processing for reproducingmore correct color by conducting matrix operation of 3×3 to the tonevalue of each pixel of the data that has undergone the pixelinterpolation. The filter processing section conducts filter processingsuch as sharpness adjustment or noise removal processing to the datathat has undergone the color conversion processing. The gamma correctionsection conducts processing to correct tone characteristics at the timeof outputting an image. Specifically, the gamma correction sectionconducts gamma correction to the data that has undergone the filterprocessing, and the gamma correction is for correcting color shown bythe tone value of output data of the image capturing sensor 14 by agamma function corresponding to color characteristics in the displaysection 20. The resizing processing section sequentially refers to thedata that has undergone the gamma correction processing to be recordedin the line buffer of the buffer 15, and resizes it to a desired size inaccordance with the record size of image data on the removable memory orthe screen size of the display section 20. When resizing is finished inthe resizing processing section, the image data DD that has undergoneeach image processing in the image processing section 80 can begenerated.

The image data DD is temporarily stored in the buffer 15. In the case ofa live view display, the image data generation section 81 notifies thedisplay control section 62 of the above-described progress informationat a timing when outputting the image data DD of one line to the buffer15 is finished (although various embodiments of the progress informationare possible as described above, the present embodiment treats the pulsesignal that shows the timing when outputting the image data of one lineof a next display target line to the buffer 15 is finished as theprogress information). When the display control section 62 determinesthat the next display target line is ready to be displayed based on theprogress information, the display control section 62 outputs thehorizontal synchronization signal DHsync to the display section 20. Theimage data DD temporarily stored in the buffer 15 is delivered by theimage data output section to the display section 20 sequentially perline, and displayed on the display section 20 at a timing defined by thehorizontal synchronization signal DHsync. As a result, an image of anobject captured by the image capturing sensor 14 is displayed on aliquid crystal panel of the display section 20. Also, the image dataoutput section outputs OSD data recorded on a frame memory of the buffer15 as the image data DD to the display section 20 sequentially per linefor the display on the display section 20. As a result, letters such asimage capturing conditions are displayed on the liquid crystal panel ofthe display section 20. In the case of actual image capturing, the imagedata DD generated and temporarily stored in the buffer 15 is deliveredby the image data output section to the recording section 30, andrecorded on the removable memory attached to the recording section 30.

Processing conducted by the image processing section 80 includes aprocess to output an evaluation value for AE (Automatic Exposure)processing and a process to output an evaluation value for AF (AutomaticFocus) processing. Specifically, the image processing section 80 canspecify an evaluation value (such as an average value of luminance) forevaluating the brightness of a pixel contained in a predetermined lightmeasurement area set within an image capturing range of the imagecapturing sensor 14, and output it as an evaluation value for AEprocessing. The image processing section 80 can also specify anevaluation value (such as a value showing the magnitude of contrast) forevaluating the degree of focusing a pixel contained in a predetermineddistance measurement area set within the image capturing range of theimage capturing sensor 14, and output it as an evaluation value for AFprocessing. Further, the image processing section 80 has a processingsection that achieves a common image processing function such as AWB(automatic white balance function) required by a digital camera.

In order to capture an image for the record by the image capturingdevice 1 according to the present embodiment (actual image capturing),the charge storing time is controlled by combining the shutter 13 as amechanical shutter and an electronic shutter of the image capturingsensor 14. Specifically, in the case of actual image capturing in thepresent embodiment, exposure time is controlled by an electronic frontcurtain—mechanical rear curtain shutter method in which an exposure isstarted by the electronic shutter of the image capturing sensor 14 andended by the light shielding curtain of the shutter 13. Morespecifically, in the case of actual image capturing, an exposure isstarted by the electronic shutter sequentially per line, and lightshielding by the mechanical shutter is started so as to shield lighteach line at a timing when exposure time per line becomes apredetermined shutter speed (second). In the case of image capturing fora live view display, exposure time (that is, charge storing time) iscontrolled by an electronic shutter method. Specifically, both of thefront curtain and the rear curtain are controlled by the electronicshutter.

A removable memory that is not shown in the drawing can be inserted intothe recording section 30. Information can be recorded on the removablememory, and information can be read out from the removable memory in astate where the removable memory is inserted into the recording section30. Image data generated by actual image capturing is recorded on theremovable memory.

1-2. Image Capturing Processing

Next, image capturing processing in the present embodiment will bedescribed in detail. FIG. 2 is a flow chart of image capturingprocessing started when an image capturing mode is selected by a userafter the power of the image capturing device 1 is turned on and aninitializing process is finished. In the image capturing device 1, alive view of an object is displayed on the display section 20, and auser waits for a shutter chance while observing the live view displayand issues an instruction to capture an image for the record. The CPU 70conducts preparation processing for the live view display in stepsS100-S105 in the image capturing processing,

More specifically, the CPU 70 opens the shutter 13 (step S100). The CPU70 outputs a control signal to the shutter control section 50, andplaces the shutter 13 in a state of being retained without interruptingthe light path. The CPU 70 adjusts the diaphragm 12 to have apredetermined aperture (step S105). In the present embodiment,explanations will be made on the assumption that image capturing for alive view display or actual image capturing is conducted giving priorityto the diaphragm. The CPU 70 may output a control signal to thediaphragm driving section 12 a, and may control the aperture tocorrespond to a diaphragm value designated by a user's operation to theoperating section 40, for example. The aperture may be controlled tocorrespond to a default diaphragm value that is determined with respectto each image capturing mode beforehand. Incidentally, control of thediaphragm 12 may be conducted before the shutter 13 is opened.

Next, the CPU 70 starts image capturing and displaying (step S110). FIG.3A is a diagram showing a screen of the liquid crystal panel of thedisplay section 20 according to the present embodiment. The displayscreen is constructed by an object image display region R1 and aninformation display region R2. The object image display region R1 is aregion for displaying image data generated based on output data outputfrom the image capturing sensor 14. The information display region R2 isa region for displaying information such as image capturing conditionswith letters or figures. In FIG. 3A, “o” represents a height of theobject image display region R1 (the number of lines), and “p” representsa height of the information display region R2 (the number of lines).

FIG. 3B is a timing chart that simplifies a charge storing timing of animage capturing target line in the image capturing sensor 14 and adisplay timing of a display target line corresponding to the imagecapturing target line. Since the image output from the image capturingsensor 14 is resized into a size corresponding to the object imagedisplay region R1 in the resizing processing section, the imagecapturing target line and the display target line do not necessarilycorrespond to 1:1 (for example, image data of the display target line ofone line can be generated from output data corresponding to a pluralityof image capturing target lines). However, in the present embodiment,for simplicity, explanations will be made on the assumption that theimage capturing target line and the display target line correspond to1:1 (the image capturing target line that outputs data for generatingimage data of one line of the object image display region R1 (the numberof the lines is “o”) shown in FIG. 3A is one line).

In FIG. 3B, a first amount of time T1 represents charge storing time inan image capturing target line. A second amount of time T2 representstime from generation of the image data DD by the image data generationsection 81 based on the output data SD of the image capturing targetline until a start of a display of the generated image data DD in adisplay target line. Specifically, the second amount of time T2 includestime (A) of reading output data from the image capturing sensor 14, time(B) of generating image data based on output data, and time (C) offorwarding the generated image data to the display section 20 until astart of a display. When the image data generation section 81 finishesgenerating the image data DD and outputting it to the buffer 15, theimage data generation section 81 outputs the progress information to thedisplay control section 62, and the display control section 62 starts adisplay of the image data DD of a display target line corresponding tothe progress information. A third amount of time T3 refers to time froma start of a display of the display target line in the current frameuntil a renewal of the display of the display target line in the nextframe, and corresponds to the vertical synchronization period per frameshown by the frame rate of the display section 20. In other words, thelength of the third amount of time T3 is equal to the length of a periodfrom output of a horizontal synchronization signal (DHsync) that definesa start of a period (horizontal synchronization period) to display imagedata of the display target line until output of a horizontalsynchronization signal (DHsync) that defines a start of a period(horizontal synchronization period) to display image data of the displaytarget line in the next frame.

In the present embodiment, the total time of the first amount of time T1and the second amount of time T2 is referred to as display delay time.Since the time (B) is variable with respect to each line, the secondamount of time is also variable. However, since the maximum value of thetime (B) can be known at the design stage, the maximum value of thesecond amount of time can also be known. In the present embodiment, themaximum value of the second amount of time is treated as the secondamount of time T2. Also, in the present embodiment, the charge storingtime in each image capturing target line is controlled to be the firstamount of time T1≦(the vertical synchronization period−the second amountof time T2). The timing control section 60 controls the frame rate ofthe display section 20 to be equal to the frame rate of the imagecapturing sensor 14. As described above, since the time (B) is variablewith respect to each line, the length of the horizontal synchronizationperiod of the object image display region R1 is variable. By adjustingthe length of the horizontal synchronization period of each line of theinformation display region R2 (for example, by making the horizontalsynchronization period of the information display region R2 shorter thanthe horizontal synchronization period of each line of the object imagedisplay region R1 when the horizontal synchronization period of theobject image display region R1 is relatively late) and displaying, theframe rate of the display section 20 can be synchronized with the framerate of the image capturing sensor 14 (the length of the verticalsynchronization period of the display section 20 can be made equal tothe length of the vertical synchronization period of the image capturingsensor 14). OSD data displayed in the information display region R2 canbe generated beforehand and recorded on the buffer 15 irrespective ofoperation of the image capturing sensor 14. Therefore, even if a displaybased on the OSD data is conducted with the short horizontalsynchronization period, an appropriate display can be conducted withoutcausing overtaking in reading out of data.

In the present embodiment, the frame rate of the image capturing sensor14 in a live view is driven at 100 fps. The following explanations willbe made on the assumption that the frame rate of the display section 20is also driven at 100 fps because the display section 20 is controlledto be synchronized with the image capturing sensor 14. When the framerate is 100 fps, the vertical synchronization period is 10 ms. Thesensor control section 61 generates a vertical synchronization signal(SVsync) per 10 ms. Accordingly, when the maximum value of the secondamount of time T2 is, for example, 3 ms, the first amount of time T1 iscontrolled to be equal to or less than 7 ms.

The CPU 70 conducts AE processing for a live view in conjunction withimage capturing and displaying (step S115). Specifically, when the imageprocessing section 80 outputs an evaluation value for conducting AEprocessing for a live view based on image data generated in step S110,the CPU 70 conducts feedback control of the charge storing time (T1) toachieve an appropriate exposure by outputting a control signal to thesensor control section 61 and adjusting the charge storing time (T1)such that the evaluation value is within an appropriate range determinedin advance.

FIG. 4 shows one example of a program diagram for automatic exposure(AE) control showing a combination of charge storing time (Tv) and ISOsensitivity (Sv) in a case where the diaphragm (Av) is fixed at F4.0 (asshown in FIG. 4, the image capturing device 1 can select 1-1/8000 as thecharge storing time (Tv), and can select 100-6400 as the ISO sensitivity(Sv). Therefore, in a case where all combinations thereof can beselected, the image capturing device 1 can control the amount of theexposure to be 17 EV to −2 EV).

In the present embodiment, explanations will be made on the assumptionthat the aperture of the diaphragm 12 has been controlled to have a sizecorresponding to F4.0 (step S105). In a case where it is determined thatthe charge storing time, that is, the first amount of time T1 is equalto or less than 7 ms as described above, the combination of (Sv, Tv)corresponding to 42(=6×7) intersection points within a region enclosedby a dashed line 4 a of FIG. 4 can be selected, and the selectable rangeof the charge storing time is 1/8000-1/250. Also, the selectable rangeof the ISO sensitivity is 100-6400. AE processing becomes possible in arange of EV 17-EV 6 by changing the ISO sensitivity within 100-6400 andchanging the charge storing time within 1/8000 s (approximately 0.125ms)-1/250 s (approximately 4 ms).

However, since a combination in which the value of the ISO sensitivityis larger among a plurality of combinations that achieve the same EVvalue deteriorates the image quality, the present embodiment uses aprogram diagram (a thick line in FIG. 4) that selects a combination inwhich the value of the ISO sensitivity is as small as possible among aplurality of combinations that achieve the same EV value within thedashed line 4 a. The thick line shown in FIG. 4 is set such that pointsshown by black circles on the thick line are combinations in which theISO sensitivity is as small as possible among combinations that achieveEV 17-EV 6.

In FIG. 4, the charge storing time (Tv) is shown by 1, 1/2, 1/4, 1/8,1/15, 1/30 . . . 1/8000. Strictly, however, the number of seconds shownby 1/2^(n) (0≦n≦13) is used as the charge storing time. For example,1/250 means 1/256 s (approximately 3.9 ms) in a strict sense, and 1/500means 1/512 s (approximately 1.95 ms) in a strict sense.

Here, for example, when the luminance value as the evaluation valueoutput from the image processing section 80 shows an underexposure of 1EV with respect to the target luminance value to achieve an appropriateexposure in a case where the combination of (Sv, Tv) is (800, 1/250),the CPU 70 controls the combination of (Sv, Tv) to be (1600, 1/250).That is, the ISO sensitivity (gain) is increased from the state of (800,1/250). With this, image capturing can be conducted with an appropriateexposure in a state where the charge storing time is maintained to beequal to or less than 1/250 s.

When it turns out that EV 8 is an appropriate exposure in a case ofmaking selections from the 42 combinations contained in the dashed line4 a, the combination of 6400 as the upper limit of the ISO sensitivityin the image capturing device 1 and 1/1000 s as the charge storing timecan be selected. In such a case, “the shortest charge storing time thatachieves an appropriate exposure when the gain is increased to an upperlimit” is 1/1000. The explanations will go back to the flow chart ofFIG. 2.

Next, the CPU 70 determines whether the shutter button is pressedhalfway or not (step S120), and repeats the processing of step S110 tostep S115 until it is determined that the shutter button is pressedhalfway. On the other hand, when it is determined that the shutterbutton is pressed halfway in step S120, the CPU 70 prepares for actualimage capturing in step S125 to step S135. Here, since step S125 to stepS130 are the same processing as step S110 to step S115, explanationsthereof are omitted.

In AF processing of step S135, when the image processing section 80outputs an evaluation value for conducting AF processing based on imagedata generated in step S125, the CPU 70 acquires the evaluation value.Then, the CPU 70 outputs a control signal to the lens driving section 11a based on the evaluation value, and conducts focus adjustment by movingthe lens 11 so that the evaluation value is in a predetermined focusingrange.

Next, the CPU 70 determines whether the halfway pressing of the shutterbutton is released or not (step S140). When it is determined that thehalfway pressing of the shutter button is released, the CPU 70 conductsthe processing of step S110 and the subsequent steps again so as tocontinue the live view display. On the other hand, when it is notdetermined that the halfway pressing of the shutter button is released,the CPU 70 further determines whether the shutter button is fullypressed or not (step S145). When it is not determined that the shutterbutton is fully pressed, the processing of step S125 and the subsequentsteps are repeated.

While steps S110-S135 are repeated, therefore, a live view is displayedon the display section 20. FIG. 5 is a timing chart showing a chargestoring timing (SD1-SD4) by the image capturing sensor 14, a processingtiming (P1-P4) by the image data generation section 81 and the like, anda display timing (DD1-DD4) by the display section 20 for a live viewdisplay. In FIG. 5, parallelograms assigned with identifiers of SD1-SD4show the charge storing timing in each line from the first frame to thefourth frame, respectively. An upper side “a” of each parallelogramshows the charge storing time (=the first amount of time T1) of a topline among effective lines (lines that output data for generating imagedata to be displayed in the object image display region R1) of the imagecapturing sensor 14. A lower side “b” shows the charge storing time in abottom line among the effective lines of the image capturing sensor 14.A height “e” shows the line number of the effective lines of the imagecapturing sensor 14. A line segment that is in parallel with the upperside “a” and the lower side “b” in which a left side “c” and a rightside “d” are both ends thereof shows the charge storing time in eacheffective line of the image capturing sensor 14. The line segment is notshown in the drawing. The left side “c” shows a charge storing starttiming in each effective line of the image capturing sensor 14. Theright side “d” shows a charge storing end timing in each effective lineof the image capturing sensor 14. Specifically, charge storing isstarted in a corresponding line by outputting a reset signal SHReset forthe line to the image capturing sensor 14 at a timing shown by theintersection point between the left side “c” and the line segment ofeach line. The output data SD is read out from the photoelectricconversion element of a corresponding line at a timing shown by theintersection point between the right side “d” and the line segment ofeach line during the horizontal synchronization period defined by thehorizontal synchronization signal SHsync that is not shown in thedrawing.

A line segment that is in parallel with an upper side “f” and a lowerside “g” of each of parallelograms assigned with identifiers of P1-P4 inwhich a left side “h” and a right side “i” of each parallelogram areboth ends thereof shows processing time (that corresponds to the secondamount of time T2 in FIG. 3B) from generation of the image data DD basedon the output data SD of each line in which charge storing is finishedat a timing shown by the right side “d” of SD1-SD4 until a start of adisplay on the display section 20. A height “j” shows the line number ofprocessing. In the present embodiment, for simplicity of theexplanation, the line number shown by the height “e”, the line number ofprocessing shown by the height “j”, and a line number shown by a height“o” described below are the same.

Parallelograms assigned with identifiers of DD1-DD4 show the displaytiming of the object image display region R1 from the first frame to thefourth frame, respectively. OSD1-OSD3 show the display timing of theinformation display region R2 from the first frame to the third frame,respectively. A height “o” as a distance from an upper side “k” to alower side “l” shows a line number of the object image display regionR1. A height “p” shows a line number of the information display regionR2. The upper side “k” shows time to continue the display in the topline of the object image display region R1 (time from a start of adisplay in the current frame until rewriting with new image data in thenext frame). A left side “m” shows a display start timing, and a rightside “n” shows a display end timing. The display end timing “n” in thecurrent frame coincides with the display start timing “m” in the nextframe. The left side “m” coincides with the timing of the right side “i”of P1-P4. The lower side “l” shows time to continue the display in thebottom line of the object image display region R1. A line segment thatis in parallel with the upper side “k” and the lower side “l” in whichthe left side “m” and the right side “n” are both ends thereof shows thedisplay continuance time in each line of the object image display regionR1.

In OSD1-OSD3, a left side “e” shows a display start timing, and a rightside “s” shows a display end timing. The slope of the left side “r” andthe right side “s” is sharper than that of the left side “m” and theright side “n” in DD1-DD4. This means that the interval to generate ahorizontal synchronization signal DHsync for displaying the informationdisplay region R2 is shorter than the interval to generate a horizontalsynchronization signal DHsync for displaying the object image displayregion R1, and the display of the information display region R2 is at ahigher speed than the display of the object image display region R1. Inthis manner, the images of the object image display region R1 and theinformation display region R2 can be renewed within one verticalsynchronization period Td.

As described above, according to the present embodiment, in imagecapturing for a live view display, the charge storing time is controlledsuch that the display delay time ΔT shown by the charge storing time(the first amount of time T1)+the processing time (the second amount oftime T2) is equal to or less than the vertical synchronization period Ts(=Td), and thus the display delay time can be reduced intentionally.Since the timing to read out the stored charge (the right side “d” ofSDn) is determined based on the vertical synchronization period Tsdefined by the vertical synchronization signal SVsync, the length of thecharge storing time (the upper side “a” of SDn) is adjusted by changingthe position of the timing to start charge storing (the left side “c” ofSDn) in a time axis direction. Incidentally, the display delay time ΔTcan be measured by a method disclosed in Japanese Patent Application No.2012-226674, Japanese Patent Application No. 2012-226675, and JapanesePatent Application No. 2012-226676. Also, the time shown by(ΔT+T3)=(T1+T2+T3) can be measured by the above-described method.According to the investigation made by the inventors of the presentinvention, it turned out that a practical range to make it difficult foran observer to subjectively perceive a delay in a live view display isat least (T1+T2+T3)≦33.3 ms, and the range is preferably (T1+T2+T3)≦20to 25 ms. In the case of the present embodiment, (T1+T2+T3) isapproximately 4 ms+3 ms+10 ms=approximately 17 ms, and good results canbe obtained. Also, the inventors confirmed that the value of the firstamount of time T1 should be equal to or less than 8 ms and should be assmall as possible. When the first amount of time T1 is set to beapproximately 16 ms in a case where the vertical synchronization periodis 60 fps, a blur occurs as well as a delay. 16 ms corresponds to ashutter speed of 1/60, and corresponds to a speed in which an imagecapturing blur easily occurs with respect to a moving object. 8 mscorresponds to a shutter speed of 1/125, and corresponds to a speed inwhich an image capturing blur does not easily occur. It can be said that4 ms (that corresponds to a shutter speed of 1/250) that is furthershorter than 8 ms is a shutter speed that achieves image capturing witha fewer object blur. Accordingly, when the first amount of time T1 isset to be equal to or less than 8 ms, it is possible to conduct imagecapturing in which no object blur occurs and a display delay is small.

The inventors confirmed that the image capturing device 1 of the presentembodiment using a method in which a line determined by progressinformation to be ready for a display of image data is sequentiallydisplayed on the display section 20 can achieve 6 ms (±4 ms) as ΔT(=T1+T2). The inventors also confirmed that the image capturing device 1can achieve 16 ms (±4 ms) as (ΔT+T3)=(T1+T2+T3).

The explanations will go back to the flow chart of FIG. 2.

When it is determined that the shutter button is fully pressed in stepS145, the CPU 70 determines charge storing time for actual imagecapturing (for image capturing of an image to be recorded. Regarding thepixel number for actual image capturing, an image is captured withhigher resolution (such as 18000000 pixels) compared to a live view) byconducting AE processing for actual image capturing (step S150). Animage to be recorded is captured with the determined charge storingtime, and recorded on the removable memory (step S155). Specifically,the CPU 70 outputs a control signal to the sensor control section 61 soas to start charge storing sequentially per line in the image capturingsensor 14, outputs a control signal to the shutter control section 50,and drives the shutter 13 at a timing that allows the charge storingtime of each line of the image capturing sensor 14 to be time determinedby step S150 in a state where the position of the focus and the apertureof the diaphragm 12 set in step S105 are maintained. As a result, theimage processing section 80 generates image data while using the buffer15 based on the output data output from the image capturing sensor 14.The CPU 70 forwards the generated image data to the recording section30, and the data is recorded on the removable memory that is not shownin the drawing. When the image capturing is ended, it goes back to stepS100 for next image capturing.

In AE processing for actual image capturing of step S150, a programdiagram different from FIG. 4 is used. In the present embodiment, the AEprocessing for actual image capturing is conducted in a state where thediaphragm is fixed at 4.0, for example (it is called diaphragm priorityautomatic exposure processing). Regarding the ISO sensitivity, a valueset by a user beforehand (or a default value corresponding to the kindof an image capturing mode) is selected. In the AE processing for actualimage capturing, therefore, the charge storing time can be selectedbetween 1/8000 s-1 s corresponding to the image capturing environment.In step S150, the charge storing time is selected to achieve an EV valuethat is determined to be an appropriate exposure in the last step S130(immediately before the shutter button is fully pressed) among therepeated step S130 in which the AE processing for a live view wasconducted. For example, when the value of the ISO sensitivity set by auser (or a default value corresponding to the kind of an image capturingmode) is 100 and it turned out that the appropriate exposure is EV 8,since the AE processing is conducted in a state where the diaphragm isfixed at 4.0 in the present embodiment, 1/15 s is selected as the chargestoring time for actual image capturing (see the white circle in FIG.4).

Specifically, when an image for the record is captured in the same imagecapturing environment, 1/15 s is selected as the charge storing time.When image capturing for a live view display is conducted, 1/250 s thatis higher-speed (shorter) time than 1/15 s is selected as the chargestoring time. Accordingly, in the image capturing device 1, the displaydelay time is reduced in a live view display by conducting imagecapturing for a live view display with such short charge storing timethat is not selected when an image for the record is captured in thesame image capturing environment.

2. Other Embodiments

The technical scope of the present invention is not limited to theabove-described embodiment. It is apparent that various changes andmodifications can be made without substantially departing from thesubject matter of the present invention. For example, a live view modeselecting switch may be provided to allow a user to select a first modethat prioritizes reduction in the display delay time over image qualityof an image displayed on the display section based on image data or asecond mode that prioritizes image quality of an image over reduction inthe display delay time. When the first mode is selected, charge storingin an image capturing target line may be started such that the firstamount of time is equal to or less than the vertical synchronizationperiod minus the second amount of time as described in the firstembodiment. When the second mode is selected, it may be possible toprioritize the ISO sensitivity set by a user (or a default), and conductAE processing by changing the diaphragm or the charge storing time asappropriate.

In the above-described embodiment, the charge storing time is selectedsuch that the first amount of time is selected to be equal to or lessthan the vertical synchronization period minus the second amount of timeboth before the shutter button is pressed halfway and in a state ofbeing pressed halfway. However, before the shutter button is pressedhalfway, it may be possible to conduct processing similar to theabove-described second mode that prioritizes the image quality. In thestate of being pressed halfway, it may be possible to conduct processingsimilar to the above-described first mode that prioritizes reduction inthe display delay time. Specifically, since it is considered that thestate where the shutter button is pressed halfway is a state where auser waits for a shutter chance, a live view is presented with a smallerdelay with respect to movement of an object in the state where theshutter button is pressed halfway. As a result, a user can observesubtle movement of an object in the state where the shutter button ispressed halfway, and the user can capture an image of the object at anappropriate timing without missing a shutter chance.

In the program diagram of FIG. 4, an exposure can be controlled with 1EV increments. However, it may be possible that an exposure can becontrolled with 1/3 EV increments by changing the charge storing timewith 1/3 EV increments. FIG. 6A shows an example of a program diagram ina case where the charge storing time (Tv) can be changed with 1/3 EVincrements. It may be possible that the ISO sensitivity (Sv) can also bechanged with 1/3 EV increments. FIG. 6B shows an example of a programdiagram in a case where both of the charge storing time (Tv) and the ISOsensitivity (Sv) can be controlled with 1/3 EV increments. By conductingcontrol with 1/3 EV increments, an exposure in a live view display canbe switched smoothly. Incidentally, when the charge storing time (Tv),for example, from 1/250 to 1/500 is controlled with 1/3 EV increments,the control is conducted with increments of 1/256, 1/322.5, 1/406.4, and1/512. Also, when the ISO sensitivity (Sv), for example, from 100 to 200is controlled with 1/3 EV increments, the control is conducted withincrements of 100, 126, 159 and 200. It may also be possible that theISO sensitivity (Sv) can be controlled with smaller increments than 1/3EV. FIG. 7 shows an example of a program diagram in a case where thecharge storing time (Tv) can be controlled in EV 17 to EV 12 with 1/3 EVincrements, and the ISO sensitivity (Sv) can be controlled in EV 12 toEV 6 with smaller increments than 1/3 EV.

In the program diagrams shown in FIG. 4, FIG. 6, and FIG. 7, AEprocessing can be conducted within a range of EV 17 to EV 6 while thediaphragm 12 is fixed. However, by changing the diaphragm value fromF4.0 to F2.8-F2.0 while (Sv, Tv) is fixed, for example, at (6400,1/250), EV 5 and EV 4 can be included in the control range of the AEprocessing.

In the first embodiment, the explanations were made on the assumptionthat the image capturing target line and the display target linecorrespond to 1:1. However, in a case where image data of one line ofthe display section 20 is generated based on output data of “z” lines(“z” is a natural number equal to or more than 2) of the image capturingsensor 14, for example, the average of the charge storing time in eachline included in the “z” lines of the image capturing sensor 14 may beused as the “first amount of time” (since the charge storing time ineach line is the same, the average of the charge storing time in eachline is equal to the charge storing time in each line). In such a case,as the “second amount of time”, it may be possible to use time from anend of charge storing in the first line among the “z” lines of the imagecapturing sensor 14 until generation of image data of one line fromoutput data of the “z” lines after an end of charge storing in thez^(th) line and a start of displaying image data of one line of thedisplay section 20 that corresponds to the “z” lines of the imagecapturing sensor 14. FIG. 8A shows the first amount of time T1, thesecond amount of time T2, and the display delay time ΔT in this case (InFIG. 8A, “z” is 2).

Also, for example, as the “first amount of time”, it may be possible touse time from a start of charge storing in the first line among the “z”lines of the image capturing sensor 14 until an end of charge storing inthe z^(th) line among the “z” lines. In such a case, as the “secondamount of time”, it may be possible to use time from an end of chargestoring in the z^(th) line among the “z” lines of the image capturingsensor 14 until a start of displaying image data of one line of thedisplay section 20 that corresponds to the “z” lines of the imagecapturing sensor 14. FIG. 8B shows the first amount of time T1′, thesecond amount of time T2′, and the display delay time ΔT in this case(In FIG. 8B, “z” is 2).

Further, in the image capturing device according to the embodiment, thecontrol unit can achieve an appropriate exposure by increasing a gain ofthe image capturing sensor in a case where an exposure is anunderexposure compared to an appropriate exposure when the first amountof time is controlled to be equal to or less than the verticalsynchronization period minus the second amount of time.

As a result, it is possible to display a live view with an appropriateexposure even in a case where the first amount of time (the chargestoring time) is controlled intentionally to be short.

In the image capturing device according to the embodiment, the controlunit can select an amount of time equal to or more than shortest chargestoring time that achieves an appropriate exposure when the gain isincreased to an upper limit as the first amount of time.

As described above, the exposure can be adjusted to be an appropriateexposure by increasing the gain of the image capturing sensor in a casewhere an exposure is an underexposure compared to an appropriateexposure when the first amount of time is controlled to be equal to orless than the vertical synchronization period minus the second amount oftime. In image capturing for a live view display, an amount of timeequal to or more than shortest charge storing time that achieves anappropriate exposure when the gain is increased to an upper limit andequal to or less than the vertical synchronization period minus thesecond amount of time can be selected as the first amount of time (thecharge storing time).

Further, in the image capturing device according to the embodiment, thecontrol unit can select charge storing time that meets theabove-described conditions as the first amount of time based on aprogram diagram that defines a combination of control values to controlan exposure in the image capturing device and at least defines acombination of the charge storing time as a control value and the gainas a control value. The above-described conditions refer to being equalto or more than the shortest charge storing time that achieves anappropriate exposure when the gain is increased to the upper limit andequal to or less than the vertical synchronization period minus thesecond amount of time.

Specifically, the control unit does not need to have a mechanism thatconducts time adjustment for optional charge storing time. The displaydelay time can be reduced and the exposure can be controlled byselecting the charge storing time that meets the above-describedconditions based on the program diagram that defines a combination ofcontrol values to control an exposure beforehand.

Further, in the image capturing device according to the embodiment, thecontrol unit selects an amount of time less than shortest charge storingtime that achieves an appropriate exposure when an image to be recordedis captured in the same image capturing environment as the first amountof time that is charge storing time in image capturing for a live viewdisplay.

Specifically, the image capturing device according to the embodimentreduces the display delay time in a live view display by conductingimage capturing for a live view display with such short charge storingtime that is not selected when an image to be recorded is captured inthe same image capturing environment (environment in which thebrightness of an object is the same).

Further, in the image capturing device according to the embodiment, anamount of time equal to or less than 8 ms can be selected as the firstamount of time.

When the vertical synchronization period is 60 fps-120 fps, it ispossible to obtain good results by selecting an amount of time equal toor less than 8 ms as the first amount of time.

Further, the image capturing device according to the embodiment may havea live view mode selecting unit that allows a user to select a firstmode or a second mode. The first mode prioritizes reduction in thedisplay delay time over image quality of an image displayed on thedisplay section based on image data. The second mode prioritizes imagequality of an image displayed on the display section based on image dataover reduction in the display delay time. In such a case, when the firstmode is selected, the control unit starts charge storing of an imagecapturing target line such that the first amount of time is equal to orless than the vertical synchronization period minus the second amount oftime.

The needs of a user regarding a live view display can be met by allowinga user to select the first mode that prioritizes reduction in thedisplay delay time over image quality of an image displayed on thedisplay section or the second mode that prioritizes image quality of animage over reduction in the display delay time. Specifically, when thefirst mode is selected, the charge storing time and the gain areselected as described above. Although a noise component is increased andthe image quality is deteriorated in a case of increasing the gain toachieve an appropriate exposure, the display delay time can be reduced,and thus the needs of a user who selected the first mode can be met.When the second mode is selected, it cannot be expected to reduce thedisplay delay time to be less than the display delay time at the time ofselecting the first mode because the charge storing time is not selectedbased on the above-described design concept. However, when the displaydelay time is not less than the display delay time at the time ofselecting the first mode, the gain becomes a smaller value than that atthe time of selecting the first mode in the same image capturingenvironment. Therefore, a noise component becomes smaller than that atthe time of selecting the first mode, and the image quality is improvedcompared to the quality at the time of selecting the first mode.Consequently, the needs of a user who selected the second mode can bemet.

Incidentally, in image capturing for a live view in a state where ashutter button is not pressed, for example, the charge storing time maybe selected in the second mode that prioritizes the image quality. Inimage capturing for a live view in a state where a shutter button ispressed halfway, the charge storing time may be selected in the firstmode that prioritizes reduction in the display delay time.

Further, the technique to satisfy the first amount of time≦(the verticalsynchronization period−the second amount of time) in image capturing fora live view display according to the embodiment can be implemented as aprogram or a method. Also, the above-described device, program, ormethod can be implemented as a single device, or implemented by using acommon part in a device having a complex function, and various kinds ofembodiments are included.

An image capturing device according to the embodiment has an image datageneration unit, a display control unit, and a control unit. The imagedata generation unit generates image data per line of a display section(per one line or per a plurality of lines) based on an output of animage capturing sensor in which a start and an end of charge storing arecontrolled per line. The display control unit causes the display sectionto display generated image data sequentially per line (per one line orper a plurality of lines). The control unit ends charge storing after afirst amount of time passes since charge storing of an image capturingtarget line is started, and starts displaying image data of a displaytarget line corresponding to the image capturing target line after asecond amount of time passes since charge storing of an image capturingtarget line is ended. In such a case, the second amount of time refersto time required for starting displaying image data in a display targetline after charge storing of an image capturing target line is ended.The second amount of time includes time for reading out output data fromthe image capturing sensor, image data generation processing time by theimage data generation unit, and time from forwarding generated imagedata to the display section until starting a display. The control unitstarts charge storing of an image capturing target line such that thefirst amount of time is equal to or less than a vertical synchronizationperiod of the image capturing sensor minus the second amount of time.

In the image capturing device of this aspect, since the first amount oftime, that is, charge storing time is controlled intentionally to beequal to or less than the vertical synchronization period minus thesecond amount of time, it is possible to reduce the time from a start ofcharge storing of an image capturing target line until a start ofdisplaying image data of a display target line corresponding to theimage capturing target line (display delay time=the first amount oftime+the second amount of time). In a case where the charge storing timethat achieves an appropriate exposure by AE processing has the samelength as the vertical synchronization period, for example, the displaydelay time (the first amount of time+the second amount of time) is equalto the vertical synchronization period plus the second amount of time,and the display delay time is not shorter than the verticalsynchronization period plus the second amount of time in a conventionaldesign concept. According to the present invention, however, the displaydelay time (the first amount of time+the second amount of time) can bemade shorter than the vertical synchronization period plus the secondamount of time. This is because the first amount of time is controlledto be equal to or less than the vertical synchronization period minusthe second amount of time.

Here, “the image capturing target line” of “the display target linecorresponding to the image capturing target line” refers to a line ofthe image capturing sensor that outputs output data for generating imagedata of a display target line. The display target line corresponding tothe image capturing target line may be one line or may be a plurality oflines.

GENERAL INTERPRETATION OF TERMS

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. An image capturing device comprising: an imagecapturing unit that captures an image at a timing based on a first framerate of the image capturing unit and outputs output data correspondingto the image after a first period; an image data generation unit thatgenerates image data based on the output data and outputs the image dataafter a second period after the first period; a display unit thatdisplays a display image based on the image data after the second periodand at a timing based on a second frame rate of the display unit; and amode selecting unit that selects a first mode or a second mode, whereinthe first mode prioritizes reduction in a display delay time of thedisplay image, the second mode prioritizes image quality of the displayimage over the reduction in the display delay time, and a total periodof the first period and the second period is less than or equal to afirst vertical synchronization period based on the first frame rate whenthe first mode is selected.
 2. The image capturing device according toclaim 1, wherein the total period of the first period and the secondperiod is less than or equal to a second vertical synchronization periodbased on the second frame rate.
 3. The image capturing device accordingto claim 1, wherein the first period corresponds to an exposure time ofthe image capturing unit, and the second period corresponds to aprocessing time of the image data generation unit for generating theimage data.
 4. The image capturing device according to claim 1, whereinthe first period corresponds to a shutter speed of the image capturingunit for capturing the image, and the second period corresponds to aprocessing time of the image data generation unit for generating theimage data.
 5. The image capturing device according to claim 1, whereinthe first period corresponds to a diaphragm value of the image capturingunit, and the second period corresponds to a processing time of theimage data generation unit for generating the image data.
 6. The imagecapturing device according to claim 3, further comprising a control unitthat controls the exposure time so that the total period of the firstperiod and the second period is less than or equal to the first verticalsynchronization period.
 7. The image capturing device according to claim4, further comprising a control unit that controls the shutter speed sothat the total period of the first period and the second period is lessthan or equal to the first vertical synchronization period.
 8. The imagecapturing device according to claim 5, further comprising a control unitthat controls the diaphragm value so that the total period of the firstperiod and the second period is less than or equal to the first verticalsynchronization period.
 9. The image capturing device according to claim6, wherein the control unit controls a gain of the image capturing unit.10. An image capturing device comprising: an image capturing unit thatcaptures an image at a timing based on a first frame rate of the imagecapturing unit and outputs output data corresponding to the image aftera first period; an image data generation unit that generates image databased on the output data and outputs the image data after a secondperiod after the first period; a display unit that displays a displayimage based on the image data after the second period and at a timingbased on a second frame rate of the display unit; and a mode selectingunit that selects a first mode or a second mode, wherein the first modeprioritizes reduction in a display delay time of the display image, thesecond mode prioritizes image quality of the display image over thereduction in the display delay time, and a total period of the firstperiod and the second period is less than or equal to a second verticalsynchronization period based on the second frame rate when the firstmode is selected.
 11. The image capturing device according to claim 10,wherein the first period corresponds to an exposure time of the imagecapturing unit, and the second period corresponds to a processing timeof the image data generation unit for generating the image data.
 12. Theimage capturing device according to claim 10, wherein the first periodcorresponds to a shutter speed of the image capturing unit for capturingthe image, and the second period corresponds to a processing time of theimage data generation unit for generating the image data.
 13. The imagecapturing device according to claim 10, wherein the first periodcorresponds to a diaphragm value of the image capturing unit, and thesecond period corresponds to a processing time of the image datageneration unit for generating the image data.
 14. The image capturingdevice according to claim 11, further comprising a control unit thatcontrols the exposure time so that the total period of the first vperiodand the second period is less than or equal to the second verticalsynchronization period.
 15. The image capturing device according toclaim 12, further comprising a control unit that controls the shutterspeed so that the total period of the first period and the second periodis less than or equal to the second vertical synchronization period. 16.The image capturing device according to claim 13, further comprising acontrol unit that controls the diaphragm value so that the total periodof the first period and the second period is less than or equal to thesecond vertical synchronization period.
 17. The image capturing deviceaccording to claim 14, wherein the control unit controls a gain of theimage capturing unit.
 18. A method for controlling an image capturingdevice comprising: an image capturing process that captures an image ata timing based on a first frame rate of the image capturing process andoutputs output data corresponding to the image after a first period; animage data generation process that generates image data based on theoutput data and outputs the image data after a second period after thefirst period; a display process that displays a display image based onthe image data after the second period and at a timing based on a secondframe rate of the display process; and a mode selecting process thatselects a first mode or a second mode, wherein the first modeprioritizes reduction in a display delay time of the display image, thesecond mode prioritizes image quality of the display image over thereduction in the display delay time, and a total period of the firstperiod and the second period is less than or equal to a first verticalsynchronization period based on the first frame rate when the first modeis selected.
 19. A method for controlling an image capturing devicecomprising: an image capturing process that captures an image at atiming based on a first frame rate of the image capturing process andoutputs output data corresponding to the image after a first period; animage data generation process that generates image data based on theoutput data and outputs the image data after a second period after thefirst period; a display process that displays a display image based onthe image data after the second period and at a timing based on a secondframe rate of the display process; and a mode selecting process thatselects a first mode or a second mode, wherein the first modeprioritizes reduction in a display delay time of the display image, thesecond mode prioritizes image quality of the display image over thereduction in the display delay time, and a total period of the firstperiod and the second period is less than or equal to a second verticalsynchronization period based on the second frame rate when the firstmode is selected.